Can you use use Loop-Cut tool with ngons?
Loop cut intentionally only cuts quads.

To cut across ngons you can:


Use the knife tool to cut up the face how you like.
Select 2 vertices and run join (Jkey).




Note, we have support for ths in the code, but after discussion with users, disabled it - see BMW_EDGERING_NGON
See:
http://lists.blender.org/pipermail/bf-blender-cvs/2012-March/043815.html